Christopher Tubbs created ACCUMULO-4642:
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Summary: Remove SystemConfiguration.getInstance()
Key: ACCUMULO-4642
URL: https://issues.apache.org/jira/browse/ACCUMULO-4642
Project: Accumulo
Issue Type: Improvement
Reporter: Christopher Tubbs
Assignee: Christopher Tubbs
Priority: Minor
In working with ACCUMULO-4050, I've realized that we need to do some internal refactoring
to get better control over HdfsZooInstance. This would enable better testing (because we could
inject a mock Instance more easily, and in more places). It would also allow us to reuse objects
without storing them statically in the JVM.
Fully realizing this would involve a lot of work, moving the static state to a single "context"
object constructed on server startup, and shared (in part or in whole) as needed throughout
the runtime server code.
However, I think we can get there incrementally, by starting with eliminating the SystemConfiguration.getInstance()
method. This causes SystemConfigurationFactory to also have a getInstance() method, and that
means that SystemConfigurationFactory is being used like the context object I describe, but
redundantly instead of AccumuloServerContext, or a server-specific subclass.
Eliminating SystemConfiguration.getInstance() might involve an intermediate step of adding
Instance parameters to many methods which currently take only a SystemConfigurationFactory,
because components will not be able to get the Instance from that configuration factory any
longer. However, even this intermediate step will be progress towards moving to a single shared
context object, which provides access to both the Instance and the configuration factory.
If we can move directly to the context object, that would probably be better, but it would
involve a lot more changes, in particular to the way the server code is initialized. Then
again, those changes might be good to prioritize anyway, because all our server components
seem to initialize differently, and it would be nice to rewrite their bootstrap code to follow
the same pattern.
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